The present invention relates to interconnection power cables. More particularly, the present invention relates to the passive connection and disconnection of a DC (direct current) power cable.
Complex computer systems employ numerous workstations connected to numerous peripheral computer devices. With the improvement in technology, it is common for one or more of these computing devices to require configuration changes and/or upgrades. Such changes are made to the computer device with the DC (direct current) power disconnected. In order to keep as much of the computer system operational, service personnel typically disconnect and connect the power cable of the particular computing device. This cable includes the DC power for the computer device being serviced. DC power is left on so that DC power is applied to the rest of the system. When an electronic device such as a peripheral is connected to an active computer bus, the power drawn immediately upon insertion or removal of DC power may be sufficient to cause transient voltages to appear on the bus resulting in component damage and/or bus data error. This problem is particularly acute in parallel systems sharing a common bus wherein a transient on one peripheral can cause data errors in all machines connected to the bus. Further, exposed pins can short the DC power bringing down the other bus connected devices or, worse, causing loss of data. Additionally, power on the connector with exposed pins is hazardous to personnel during connection/removal of the DC power.
The DC power as well as other computer signals are often supplied to each computer device through a plug and connector. These are commonly used in computer devices and well known to those in the art. These connectors have a plurality of male pins that mate with a corresponding female receptacles pins. Both the male and female ends may be adapted for termination of a wire harness. This arrangement of a connector plug/receptacle on the end of a wire harness is called a xe2x80x9cpendant connector.xe2x80x9d A connector with power applied is called a xe2x80x9chot-plug.xe2x80x9d It is analogous to the hot insertion and hot removal of computing devices on a powered up host computer bus.
Typically, power removal is accomplished through electromechanical circuit breakers wherein AC (alternating current) power is removed to large portions of equipment. This requires field maintenance personnel to know where these circuit breakers are located and to remember to disconnect the AC power. Even if this is accomplished, the circuit breakers often are used to power large areas including lighting circuits as well as the receptacle outlets powering the computing device of interest.
It is less disruptive to personnel using the computer equipment to disconnect low voltage DC prior to unmating of equipment connectors powering a specific computing device. In this manner the rest of the computer network remains functional during the maintenance or servicing of a particular computer device. However, the disconnection of an energized power cable poses a safety hazard for personnel and, therefore, requires extreme caution. Further, exposed power contacts may contact objects creating shorts to ground or injecting unwanted voltage transients onto the power lines. This creates a risk of loss of data and loss of compute capability.
A number of devices have been disclosed for computer bus isolation to minimize bus transients during the hot removal and hot insertion of circuit boards, peripherals, etc., e.g., such devices are described in U.S. Pat. Nos. 5,586,271 and 5,210,855. These devices are bulky and do not assure power removal and application without operator intervention.
Further, U.S. Pat. No. 2,573,920, entitled Coupled Actuated Magnetic Switch, describes a plug with an internal magnet arranged to remove AC power from a receptacle outlet containing a magnetic switch when the plug is removed therefrom. This arrangement removes high voltage AC power to prevent short circuits and hazards to personnel. It does not address removal of DC power from a pendant connector. Further, no provision is made for electronic circuitry that can be adapted to apply/remove the power in various ways such as buffering to limit inrush current or bus transients.
Other approaches that passively protect circuitry during hot connect/disconnect of connectors have required reconfiguration of the connector pins, additional circuitry external to the connector, and/or additional wires in the connector harness. One approach requires reconfiguration of the connector to have pins of different lengths. This entails creating specialized connectors with different configurations for different connector applications. Another implementation employs a mechanical interlock switch for a rack/tray assembly whereby inrush currents are managed whenever plugging and unplugging the racks/trays. This switching method is not adapted to connectors on pendant cords nor is a proximity switch employed.
The present invention employs a proximity switch to determine when mating connectors are in close proximity to each other. Proximity switches are xe2x80x9cpassivexe2x80x9d in that they rely on various types of physical phenomena such as magnetism or capacitive discharge rather than actuation by an operator. The present invention thereby provides a passive mechanism that is contained within a connector housing; requires no additional external wiring; and removes electrical power prior to connector unmating and applies power only after connection during connector mating/unmating. An LED (light emitting diode) or other indicator may be incorporated to provide visual indication of voltage condition.